The invention is in the field of luminous displays and signs, and more particularly relates to gas plasma display devices.
The production of light by the passage of electricity through gases is a well known phenomenon. Devices utilizing this phenomenon have been widely developed in the form of plasma display devices which display specific numerals, characters, symbols, graphics, and the like. The neon sign is an example of a gas discharge display device, typically including an elongated glass tube filled with neon and a pair of excitation electrodes disposed at opposite ends of the tube. In this example, the rigid tube, or envelope, defines the shape of the illumination pattern. This shape is established at the time of manufacture, and cannot be changed.
Other prior art gas discharge display devices may include a base electrode and a plurality of shaped character electrodes in direct or close contact with an electroluminescent gas within a glass envelope, for example, Nixie tubes. In such devices, selected ones of the shaped electrodes may be energized with respect to the base electrode to obtain a desired character display. Again, the shape of the illumination is predetermined by the shape of the electrode which is established at the time of manufacture of the device.
Still other forms of prior art gas discharge display devices include dielectric-bounded, gas-filled character-shaped channels within an envelope, with a suitable set of energizing electrodes. As in U.S. Pat. No. 3,621,332, a plurality of such channels may be established within a single envelope, with electrodes being arranged for selective activation of one channel at a time. Alternatively, as in U.S. Pat. No. 4,584,501, a single elongated channel may be formed in one plate of a two glass plate sandwich arrangement, with energizing channels in an adjacent plate. All of these arrangements are suitable for displaying indicia, but as with the earlier discussed prior art, the shape of the display, i.e. the channel configuration, is determined at the time of manufacture of the device.
Yet other prior art gas discharge devices include generally similar display configurations, but have an addressable matrix in which selected dot regions may be selectively energized. For example,
shown in U.S. Pat. No. 4,035,690, selected ones of overlapping orthongal sets of electrodes may be energized to generate a desired dot matrix character. In that patent, the electroluminescent gas is confined to the interior of a plurality of dielectric spheres disposed between the sets of electrodes. With the dot addressable matrix, substantial flexibility is provided in that any dot pattern graphics may be displayed, for example using conventional bit-mapped graphics techniques. However, as with the other above mentioned prior art, all possible display patterns, i.e. the electrode overlap regions, are established at the time of manufacture of the device.
Yet another form of prior art gas discharge device is disclosed in U.S. Pat. No. 3,629,654. As shown in that patent, a pair of opposed, spaced apart plates are mutually sealed at their perimeter to establish an electroluminescent gas filled cell. A transparent conductive coating is disposed on one outer surface of the cell. A movable external sheet having predetermined shaped conductive regions is pressed against the other outer surface of the cell and an ionizing signal is applied across the conductive coating and the conductive region of the external sheet to generate a visible discharge in the cell having the shape of the conductive regions of the external sheet. This two-element display thus requires a means for positioning the external sheet relative to the cell in order to establish an image.
In the prior art there are many known techniques and circuits for the interactive control of luminous and lighting devices. Many of these are commercially available as "touch control" light dimmers or switches. These generally employ circuitry that senses an external field or capacitance, as that of a human body or any of its parts, either by close proximity or by direct contact with a circuit element.
In these devices, the effect of the application of the external field or capacitance is an alteration of the circuitry's operating state, leading to an offset voltage or current internal to the circuit. This voltage or current offset is then applied to some interconnected lighting device, i.e., an incandescent lightbulb, thus changing its brightness in a response to either the duration or character of the externally applied influence.
The term "interactive" here applies to the nature of the control mechanism, it being the control loop formed by the person initiating or continuing the influence on the circuit and the circuit's response in changing the light output of the lighting device, with feedback between the light output of the lighting device and the Person. The interaction of the person with the (control mechanism/lighting device) combination results in a change in the operating parameters of the combination, i.e., a modification of the light output of the lighting device. Lighting control devices of this type may be characterized as indirect interacting, due to the indirect nature of the control influence on the lighting device itself.
It is also known in the prior art to directly interact with the method of light production, and thus directly control the lighting device. By way of example, there are certain gas plasma artistic works, such as those of the present inventor, in which an electroluminescent gaseous medium is contained in an enclosed gas tight chamber and disposed about an electrode centrally located within the chamber. When the electrode is suitably energized, a luminous plasma discharge is established from the electrode, through the chamber to a reference potential outside the chamber. With such devices, when a person touches the chamber surface, the person's body, or some part of thereof, acts as a capacitor plate and thereby allowing the passage of alternating current between the electrode and the reference potential along field lines that are directly related to the body capacitance and its point of application to the chamber wall. This capacitor effect acts as charging means for the luminescent gas, producing what is termed a capacitive discharge. When in use, the device responds to the proximity of the body, or any other such effective capacitor plate, in direct correspondence to it capacitance, and a luminous display is produced that is directly related to its distance from the central electrode.
It is an object of the present invention to provide an improved plasma display device.
Another object is to provide an improved plasma display device which may be interactively controlled, for example by a person's body capacitance, to establish a luminous plasma display.